canvas 导出图片网络失败的故障排除

canvas.toBlob()  // canvas 转blob

URL.createObjectURL() // blob生产url

 html2canvas(document.querySelector('.fizz_inject_wrap_div')).then(function(canvas) {
      canvas.toBlob(function (blob) {
        const eleLink = document.querySelector('#fizz_rm_down_link');
        eleLink.download = pageTitle + '.png';
        eleLink.style.display = 'none';
        // 字符内容转变成blob地址
        eleLink.href = URL.createObjectURL(blob);
        // 触发点击
        eleLink.click();
      },'image/png',1)
    })